Abnormal Uterine Bleeding
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Causes & Risk Factors

What causes abnormal uterine bleeding?

Many different things can cause abnormal uterine bleeding. Pregnancy is a common cause. Polyps or fibroids (small and large growths) in the uterus can also cause bleeding. Rarely, a thyroid problem, infection of the cervix or cancer of the uterus can cause abnormal uterine bleeding.

In most women, abnormal uterine bleeding is caused by a hormone imbalance. When hormones are the problem, doctors call the problem dysfunctional uterine bleeding, or DUB. Abnormal bleeding caused by hormone imbalance is more common in teenagers or in women who are approaching menopause.

These are just a few of the problems that can cause abnormal uterine bleeding. These problems can occur at any age, but the likely cause of abnormal uterine bleeding usually depends on your age.

Women in their teens, 20s and 30s

A common cause of abnormal bleeding in young women and teenagers is pregnancy. Many women have abnormal bleeding in the first few months of a normal pregnancy. Some birth control pills or the intrauterine device can also cause abnormal bleeding.

Some young women who have abnormal uterine bleeding do not release an egg from their ovaries (called ovulation) during their menstrual cycle. This is common for teenagers who have just started getting their periods. This causes a hormone imbalance where the estrogen in your body makes the lining of your uterus (called the endometrium) grow until it gets too thick. When your body gets rid of this lining during your period, the bleeding will be very heavy. A hormone imbalance may also cause your body not to know when to shed the lining. This can cause irregular bleeding (“spotting”) between your periods.

Women in their 40s and early 50s

In the years before menopause and when menopause begins, women have months when they don't ovulate. This can cause abnormal uterine bleeding, including heavy periods and lighter, irregular bleeding.

Thickening of the lining of the uterus is another cause of bleeding in women in their 40s and 50s. This thickening can be a warning of uterine cancer. If you have abnormal uterine bleeding and you’re in this age group, you need to tell your doctor about it. It may be a normal part of getting older, but it's important to make sure uterine cancer isn't the cause.

Women after menopause

Hormone replacement therapy is a common cause of uterine bleeding after menopause. Other causes include endometrial and uterine cancer. These cancers are more common in older women than in younger women. But cancer is not always the cause of abnormal uterine bleeding. Many other problems can cause bleeding after menopause. For this reason, it’s important to talk to your doctor if you have any bleeding after menopause.